Ticks, biting flies, spiders, mites, and chiggers are examples of arthropods that pierce the skin of humans and animals, causing damage to skin, blood loss, and irritation, as well as transmission of deadly infectious diseases. These factors contribute to the enormous economic losses sustained by the livestock industry. Losses in livestock production (cattle, sheep, swine, and poultry) in the U.S. due to arthropod pests were estimated at more than $3 billion. This figure does not include the cost of pest control or losses to the equine industry (see Drummond, R O et al., Control of Arthropod Pests of Livestock: A Review of Technology, CRC Press, Inc., Boca Raton, Fla., 245 pp. (1988)). Although precise figures for most countries are lacking, estimates of world-wide economic losses due to ticks and tick-borne diseases alone are in the billions of dollars.
Ticks are obligate parasites of vertebrates, feeding exclusively on blood. Most tick species have a simple life cycle with three active stages, larva, nymph and adult. All three must seek out a vertebrate animal for their meal, feed, drop off, molt to the next stage, and begin the process over again. Thus, each life stage must crawl up and through vegetation where host animals are present, cling to these animals and suck blood. Blood feeding occurs over a period of several days. The remainder of the life cycle is spent in the soil and vegetation, either in development or waiting for hosts.
Removal of pest infestations in a specific area is a formidable task. Thus, it is not surprising that no single, universally accepted method is available for this purpose. It is well established that certain chemicals, such as pheromones, can be used to attract pests to an area for elimination. Allan and Sonenshine, for instance, teach of several tick-specific pheromones in U.S. Pat. No. 6,331,297, and Bernier teaches of numerous general chemoattractants for arthropods in U.S. Pat. No. 6,800,279.
One use for these chemoattractants is to localize arthropod pests and other common pests with the intent of killing or removing them mechanically. Lenz teaches in U.S. Pat. No. 6,530,172, for instance, how to use CO2 as a chemoattractant for Diptera (such as mosquitoes and flies), an idea developed by Jablin (U.S. Pat. No. 6,675,528) to attract and incinerate them. Robinson (U.S. Pat. No. 6,718,687) developed a similar method to remove Diptera from an area, but used lactic acid as the chemoattractant and an electric fan as the killing mechanism.
With the aforementioned mechanical methods for elimination, the target pest is attracted to the vicinity of the pheromone source and is expected to become entangled in an adhesive or caught in a container. Such traps may not be effective for all pest species, especially in those cases where additional chemical or physical stimuli are necessary to induce mating. Further, pheromones (or chemoattractants) work only over a limited region (e.g., ticks are attracted over about a 15 foot radius to a point source of CO2 being released at human respiratory rates), so to reduce a species population over an area such as a typical residential or agricultural property requires many chemoattractant sources and requires them to be regularly replenished.
The use of pesticides as a method to kill arthropods that have been attracted to an area has several advantages over the mechanical killing mechanisms described above. Pesticides are robust, do not require external power, and may be cheaper to implement. Norval, for instance, describes a chemoattractant-emitting decoy containing an acaricide (U.S. Pat. No. 5,296,227) to destroy ticks, as does Sonenshine (U.S. Pat. No. 4,884,361). One interesting variation of this idea is described by Norval and Sonenshine in U.S. Pat. No. 5,357,902, in which feed is used to attract a host to a specific area, where the host is passively brushed with a suitable pesticide for eliminating ticks. Where there are multiple chemoattractant sites, either multiple reservoirs of pesticide or widespread pesticide spraying is required. Unfortunately, widespread pesticide spraying operations can pose environmental hazards for the surrounding area as well as health hazards for individuals working near the spraying facility. Further, certain pesticides may cause contamination of the host with toxic chemicals.
Robots have also been used in methods to reduce pest populations. Donaldson (U.S. Pat. No. 6,688,255) teaches a robot that can pick up insects such as fruit flies and transfer them to a holding container. Ruffner (U.S. Pat. Nos. 6,338,013 and 6,611,738) describes a multifunctional robot that can clean, mow lawns, or spray a pesticide, using GPS or radio navigational beacons to remain within a defined area. Unfortunately, because the pesticide is not directed specifically at the pest by the robot, host animals or individuals may be contaminated by the toxic materials.
One novel application of robots for targeted arthropod control is the development of a non-mobile micro machine that the pest transports to its nest, where it releases a pesticide (Creeger, U.S. Pat. No. 5,974,726), sends a locating beacon, or violently explodes (Creeger, U.S. Pat. No. 6,581,324). Unfortunately, this method would not be effective in the reduction of populations of many pests because few pests would carry the machine to their nests.
Accordingly, there is a need for an effective system and method for controlling populations of pests. In particular, a need exists for a way to more accurately target pests for extermination or capture, without adversely affecting the surrounding environment.